Ballistic print hammer and type-bearing element combination for on-the-fly printer

ABSTRACT

A printer of the kind having a print hammer and movable typecarrying members, wherein, to avoid problems of interference, each type character is associated with an element of mass m and is actuated to effect printing by the print hammer through a ballistic interposer having substantially the same mass m, and wherein the ballistic interposer is projected against the element associated with each character to transfer thereto its entire dynamic energy and is thereby arrested.

United States Patent [191 Cattaneo Apr. 23, 1974 BALLISTIC PRINT HAMMERAND [56] References Cited TYPE-BEARING ELEMENT COMBINATION UN STATESPATENTS FOR ON'THE'FLY PRINTER 2,236,663 4 1941 Adams 197/53 [75]Inventor, Sergio Camneo, voghera, Pavia, 3,289,805 12/1966K1einschmidt.... 197/53 x Italy 2,787,210 4/1957 Shepard 101/93 C3,542,182 11/1970 Langenburger... 197/18 [73] Assignee: HoneywellInformation Systems 3,371,766 5/1968 Staller 1 197/53 ltalia formerlynamed General 3,575,107 4/1971 'McDowell 101/93 Electric InformationSystems Italia, Caluso, Italy Primary Examiner-Robert E. PulfreyAssistant ExaminerE. M. Coven [22] Flled 1972 Attorney, Agent, orFirm-Fred Jacob [21] Appl. No.: 279,559

Related US. Application Data [57]. T T [63] Continuation of Ser. No. 50659 June 29 1970 A punter of the kmd having a pnm hammer andmovabandoned able typecarrying members, wherein, to avoid problems ofinterference, each type character is associated [30] Foreign ApplicationPriority Data with an element of mass m and is actuated to effect J 281969 It 1 8918/69 printing by the print hammer through a ballisticinterune a y poser having substantially the Same mass and wherein theballistic interposer is projected against the 197/53 101/93 elementassociated with each character -to transfer [58] Fie'ld 137/53 theretoits entire dynamic energy and is thereby arrested.

6 Claims, 6 Drawing Figures PATENTEDAFRN 14 3; 805.941

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SHEET 2 OF 2 ser w CATTANEO INVENI OR BALLISTIC PRINT HAMMER ANDTYPE-BEARING ELEMENT COMBINATION FOR ON-TI-IE-FLY PRINTER This is acontinuation of application $81. No. 50,659, filed June 29, 1970 nowabandoned.

BACKGROUND OF THE INVENTION This invention relates to high-speed impact,or onthe-fly, printers used in data processing systems and particularlyto high-speed serial, parallel, or serialparallel impact printers.

One form of such impact printers are known as bed printers, which printby means of one or more print elements or hammers, and a support plane,platen, or fixed printing bed. A type-bearing element consisting, forexample, of an assemblage of flexible character tongues supported by abelt is interposed between a hammer and the printing bed and is suitablymoved so that all the characters of the type-bearing element arepositioned, one after the other, at a predetermined print position.

As is known, one of the major problems in this form of printer arisesfrom interference between the print hammer and the type-bearing element,with the consequent risk of jamming or breaking the parts. This risk hasbeen reduced by suitably spacing the support tongues of the charactersalong their direction of motion, although, as is known, such spacingintroduces a substantial reduction in the printing speed.

Therefore, it is the object of this invention to eliminate thesedisadvantages of such impact printers without reducing theirperformance.

SUMMARY OF THE INVENTION The above-described interference problem iseliminated in the printer of the instant invention, by suitablydesigning the masses of the characters and the print hammer, therebyobtaining the additional advantage that the support tongues of thecharacters can be made sufficiently close' together such as to provideeven higher printing speeds.

BRIEF DESCRIPTION OF THE DRAWING The invention will be described withreference to the accompanying drawing, wherein:

FIG. 1 is a perspective view of a prior art impact printer;

FIGS. 2a, 2b, and 2c are top views which show schematically thesuccessive steps of a printing operation in the printer of FIG. 1;

FIG. 3 is a perspective view of a portion of a printer in accordancewith the invention; and

FIG. 4 is a detailed perspective view of the preferred embodiment of theprinter of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows a prior art serialplaten printer. Each of the different type characters of the printassemblage is arranged on the outer end of a flexible support tongue 1and disposed along a circumference of the assemblage.

The assemblage of tongues 1 forms a daisy, which is rotated at constantspeed by means of a motor M.

Due to the rotation of the daisy the respective ends of the tongues arepositioned one after the other in registration by an electromagnet 5.

Print hammer 3 is provided with suitable resilient return springs tourge the hammer toward a home position and with appropriate dampingmeans to eliminate vibrations and rebounds. These construction detailsare not shown in the drawing since they are not necessary for anunderstanding of the invention.

The flexible support tongues l are of rectangular cross-section and havea very small moment of inertia in the direction perpendicular to theplane of the typebearing daisy. Thus, the energy of elastic deformationrequired to bring the end of the tongue into contact with theprint-receiving member is very small. The printing is carried out byexciting electromagnet 5 at selected times, so that head 2 of hammer 3urges the outer end of the selected tongue, which bears the character tobe printed, against an inked ribbon 6, the printreceiving member 7 and aprinting bed, or platen, 8 behind member 7. The printing mechanism,comprising hammer 3 and type-bearing daisy is arranged on a carriage 9,which slides along guides 10. This printing mechanism is moved eitherincrementally or continuously so as to enable the successive printing inthe various printing positions along a print line.

FIGS. 2a, 2b, 2c, illustrate the printing operation in three successivesteps, and emphasize the relative positions assumed by the type-bearingtongues l and head 2 of print hammer 3 to demonstrate the interferenceproblem. The instant of the start of excitation of electromagnet 5 isshown in FIG. 2a. In the home position, the striking surface 11 of head2 is at a sufficient distance from platen 8 that type-bearing tongues Ican pass by freely without striking head 2. The direction of motion oftongues 1 is indicated by the arrow A. When a particular tongue 12,bearing the character selected to be printed, reaches a positionsuitably ahead of the printing position, electromagnet 5 is excited,forcing head 2 to begin to move toward platen 8. This is the situationillustrated in FIG. 2a.

During its movement toward platen 8 head 2 strikes against tongue 12,forcing tongue 12 against inked ribbon 6, print-receiving member 7 andplaten 8, FIG. 2b. At this moment tongue 12 is in precise printingposition and head 2 is close to platen 8, interposing itself betweenadjacent moving tongues 13 and 14.

If, due to some defect (a timing error, weakening of the return springs,friction, etc.) the retraction of head 2 is not carried out promptly,the next-following typebearing tongue 14 strikes against head 2, causingjamming of the type-bearing elements, as shown in FIG. 2c.

This danger is only partly reduced by chamfering either the edges ofhead 2 or of type-bearing tongues 1; therefore, this does not provide asatisfactory solution to the problem. However, in accordance with theinstant invention the problem is solved by suitably designing the massesof the type-bearing elements and the print hammer.

From the fundamental laws of mechanics it is known that in a perfectlyelastic and central impact the momentum of an isolated system ismaintained. Moreover in such as elastic, central impact between twoequal masses, one of which is stationary, the velocity of the first isentirely transferred to the second, while the first stops. The printerportion of FIG. 3 is an embodiment of such principle.

Each type character, FIG. 3, is disposed on a typebearing element 15,which has a suitable mass m,. Element is affixed by welding, brazing orother convenient method to the outer end of a flexible support tongue 1.The assemblage of flexible tongues 1, forming a type-bearing daisy, isrotated at constant angular velocity W. Print hammer 3 acts on element15, preferably by means of an interposer, or ballistic, element 16,which has a suitable mass m and is guided appropriately. For example, asshown, ballistic element 16 is supported and guided by two flexiblefingers 17 and 18, which are held by a suitable support 19 so thatballistic element 16 can move without friction. In addition, flexiblefingers 17 and 18 exercise a slight elastic-return force when ballisticelement 16 is displaced from its normal rest position.

The ballistic element 16 is projected against element 15, FIG. 3, byexcitation of electromagnet 5, which actuates hammer 3. After hammer 3strikes ballistic element 16 and imparts to it a predetermined velocityV toward type-bearing element 15, the stroke of hammer 3 is arrested,either by means of suitable stopping devices, not shown, or by closureof the air gap of the electromagnet 5.

The ballistic element 16 continues the stroke with a velocity V whichcan be considered constant, neglecting the slight reaction of fingers,l7 and 18 and strikes against type-bearing element 15. Although, element15 has a considerable peripheral velocity V perpendicular to the path ofmotion of ballistic element 16, its velocity component V in thedirection of motion of element 16 is zero before the impact.

The total momentum inherent in the system of the two masses in thedirection of motion of ballistic element 16 is m V immediately beforethe impact and becomes m V' m V, immediately after the impact.Therefore, the following equation must be satisfied:

pact, the total kinetic energy of the system is constant. Before theimpact this total kinetic energy is:

After the impact the total system kinetic energy is:

m1(V 3 V l' m2 VI22 Since the total system kinetic energy before andafter impact is constant, the following equation must be satisfied:

If, now, the two masses m and m are equal, and designated by the symbolm, equations (1) and (2) can be simplified to:

m (V g VII) "1 V2 1/2m' (V V l/2m (V V V%) and as known, the equationsare satisfied when either V, or V' is zero. Therefore, ballistic element16 stops at the instant of impact without interposing itself into thepath of the next-arriving tongue 1. Thus, the interference problem iscompletely eliminated.

The above-mentioned simplifying conditions of an isolated system and anelastic, central impact can be substantially attained in practice, usingsome construction techniques, which provide for the actual behavior ofthe printer not differing substantially from the theoretical.

It has been found by experiment that the energy required for printing acharacter with an inked ribbon commonly used in typewriters variesbetween 30,000 and 80,000 ergs., according to the surface of the typecharacter (dimensioned approximatively like a typewriter character), thequality of the print-receiving member, and the number of copies to beprinted. Moreover, the most suitable imprinting velocity must not begreater than 5 IOm/sec.

At lower velocities of 2-5m/sec a better printing quality is obtained byvirtue of less embossing of the print-receiving member. However, becausethe printing is on-the-fly; i.e., with the type-bearing element rotatingcontinuously relative to the print-receiving member, at these lowerprinting velocities the contact time between character andprint-receiving member is increased, whereby the printing ischaracterized by a more accentuated shading and by a broadening of theprinted image in the direction of rotation of the typebearing element.

From these premises it has been determined that the mass m, at the outerend of each type bearing tongue 1 can be established at 0.5 grams as acompromise solution.

The consequent projection velocity required is approximativelySm/sec.The mass of ballistic element 16 can then be 0.5 grams, or can beslightly less so as not only to avoid the danger of interference but toprovide a small inherent component of return speed for ballistic element16 after the impact.

To achieve impacts which are as central as possible, particularly in thepresence of imprecise timing, the respective masses m, and m of thetype-bearing tongues and the interposed ballistic element may beslightly displaced in the striking direction, and the striking surfaceof at least one of these two members, for example that of the ballisticelement, may be somewhat convex.

The above-described considerations are applied to the exemplary printerof FIG. 4. 64 individual typebearing elements 20 are attached by brazingto the outer ends of a set of flexible tongues 21 to form a daisymounted for rotation on a drive shaft 22. This daisy member is disposedadjacent a central stiffening plate 23.

Stiffening plate 23 extends radially close to the outer .end of tongues21 and is provided with two annular grooves 24 and 25. In outer groove25 is arranged a ring of suitable resilient material, which ringprotrudes slightly out of groove 25 to form a support for typebearingtongues 21, thereby slightly preloading such tongues. This resilientring is provided for damping the elastic vibrations of each tongue 21about its home position when it returns to this home position after aprinting operation. In addition such resilient ring establishes awell-defined, stable home position for tongues 21, which position is notinfluenced by small dynamic imbalances in the daisy, imbalances whichotherwise would cause vibrations of .the tongues.

The daisy and stiffening plate 23 are driven in rotation on shaft 22 bya motor 26, supported on a carriage member 27. Carriage member 27 slidesalong guides 28 and 29 to occupy successively all printing positionsprovided along the print line. On carriage member 27 there is alsoarranged an actuating electromagnet 30, whose movable armature 31 actsto suitably project an interposer ballistic, element 32 against atype-bearing element 20.

Armature 31 is pivoted on a pin 33 and is maintained in a rest positionagainst a stop device, which is preferably resilient and'adjustable bymeans of a screw 34. Ar-

mature 31 is urged against the stop device by a spring 35. A similarresilient stop device, adjustable by means of a screw 36, is providedfor ballistic element 32 and acts, for example, on a flat spring 37.Spring 37, together with a spring 38, form a resilient support devicefor ballistic element 32.

The devices for timing and selecting the angular position of thetype-bearing daisy are not illustrated here, their functions andstructures being well known in the art. 1

Although the printer shown in FIG. 4 relates to a serial printer and,particularly, one employing a daisyshaped type-bearing element, it isevident that the same design principles can be applied to parallel andserialparallel printers, as well as to printers employing differenttype-bearing elements, such as print bars, belts, chains and the like,wherein the characters to be printed are supported by flexible tongues,without departing from the scope and the objects of the invention.

Moreover, it is to be understood that the characters of the printer ofthe invention, and the masses associated therewith, instead of beingsupported and guided by flexible tongues, can be disposed and guidedwithin special sliding seats provided in a rigid element, each one ofthem being provided with elastic return devices.

I claim:

1. In a high speed on-the-fly printer mechanism wherein each of aplurality of different type-bearing elements is supported on arespective one of a plurality of elongated flexible tongues, and whereinone end of each of said tongues is affixed to a movable member adaptedto be driven to move said type-bearing elements in a path in a firstdirection through a printing position opposite a platen member in whichposition the elements are struck while being so driven, an actuatingapparatus comprising: hammer means selectively actuable for moving in asecond direction transverse to said first direction, an interposerelement disposed be tween said hammer means and said type-bearingelements in said printing position and having a portion thereofinterposed to be struck by said hammer means when actuated and a portionaligned for striking onthe-fly one of said type-bearing elements beingmoved along said path through said printing position, and arrestingmeans located to arrest said hammer means 6 to move substantially insaid second direction upon said portion thereof being struck by saidhammer means to strike said one of said type-bearing elements with saidanother portion, the mass of said interposer element being no greaterthan the mass of each of said typebearing elements, whereby saidinterposer element upon striking one of said type-bearing elements willtransfer its momentum to said type-bearing element without moving intosaid path.

2. The printer of claim 1, wherein said interposer element isresiliently supported.

3. The printer of claim 1, wherein said movable member is circular inshape and said type-bearing elements are driven in a circular paththrough said printing position.

4. The printer of claim 3, further including a stiffening plate mountedon said movable member for providing partial support for saidtype-bearing elements.

5. A high-speed on-the-fly printer mechanism comprising:

a plurality of different type-bearing elements,

a plurality of elongated flexible tongues each supporting a respectiveone of said type-bearing elements,

a movable member, one end of each of said tongues being affixed to saidmovable member, whereby said type-bearing elements are drivensuccessively in a path in a first direction through a printing positionand are flexurally supported by said tongues for movement in a seconddirection transverse to said first direction,

an interposer element disposed opposite said printing position, andmeans for selectively actuating said interposer element for movementballistically in said second direction transverse to said firstdirection to strike the one of said type-bearing elements being moved insaid path through said printing position on-the-fly, the mass of saidinterposer element being no greater than the mass of each of saidtype-bearing elements, whereby said interposer element' upon strikingsaid one of said type-bearing elementswill transfer its momentum to saidone of said type-bearing elements without moving into said path. v

6. A high-speed on-the-fly printer comprising in combination:

a platen,

a movable member having a plurality of type-bearing elements mountedthereon, one adjacent the other, for successive movement in a path pasta printing position on said platen, supporting means for flexurallymounting each of said typebearing elements on saidmovable memberproviding for relative movement with respect to said movable member ofsaid type-bearing elements toward and away from said platen,

an interposer element disposed in spaced relation with said platen andon the opposite side of said type-bearing elements from said platen,said interposer element being resiliently supported for relativemovement toward and away from a typebearing element disposed adjacentsaid platen printing position,

a hammer disposed adjacent said interposer member on the opposite sideof said interposer member from said type-bearing elements, and

tween said hammer and said one of said typebearing elements, each ofsaid type-bearing elements and said interposer element being so formedthat the mass of said interposer element is no greater than the mass ofeach of said type-bearing elements, whereby said interposer element uponstriking said one of said type-bearing elements will transfer itsmomentum to said one of said typebearing elements without moving intosaid path.

1. In a high speed on-the-fly printer mechanism wherein each of aplurality of different type-bearing elements is supported on arespective one of a plurality of elongated flexible tongues, and whereinone end of each of said tongues is affixed to a movable member adaptedto be driven to move said type-bearing elements in a path in a firstdirection through a printing position opposite a platen member in whichposition the elements are struck while being so driven, an actuatingapparatus comprising: hammer means selectively actuable for moving in asecond direction transverse to said first direction, an interposerelement disposed between said hammer means and said type-bearingelements in said printing position and having a portion thereofinterposed to be struck by said hammer means when actuated and a portionaligned for striking on-the-fly one of said type-bearing elements beingmoved along said path through said printing position, and arrestingmeans located to arrest said hammer means after striking said interposerelement and prior to said interposer element striking said type-bearingelement so that said interposer element is projected ballistically tomove substantially in said second direction upon said portion thereofbeing struck by said hammer means to strike said one of saidtype-bearing elements with said another portion, the mass of saidinterposer element being no greater than the mass of each of saidtype-bearing elements, whereby said interposer element upon striking oneof said typebearing elements will transfer its momentum to saidtype-bearing element without moving into said path.
 2. The printer ofclaim 1, wherein said interposer element is resiliently supported. 3.The printer of claim 1, wherein said movable member is circular in shapeand said type-bearing elements are driven in a circular path throughsaid printing position.
 4. The printer of claim 3, further including astiffening plate mounted on said movable member for providing partialsupport for said type-bearing elements.
 5. A high-speed on-the-flyprinter mechanism comprising: a plurality of different type-bearingelements, a plurality of elongated flexible tongues each supporting arespective one of said type-bearing elements, a movable member, one endof each of said tongues being affixed to said movable member, wherebysaid type-bearing elements are driven successively in a path in a firstdirection through a printing position and are flexurally supported bysaid tongues for movement in a second direction transverse to said firstdirection, an interposer element disposed opposite said printingposition, and means for selectively actuating said interposer elementfor movement ballistically in said second direction transverse to saidfirst direction to strike the one of said type-bearing elements beingmoved in said path through said printing position on-the-fly, the massof said interposer element being no greater than the mass of each ofsaid type-bearing elements, whereby said interposer element uponstriking said one of said type-bearing elements will transfer itsmomentum to said one of said type-bearing elements without moving intosaid path.
 6. A high-speed on-the-fly printer comprising in combination:a platen, a movable member having a plurality of type-bearing elementsmounted thereon, one adjacent the other, for successive movement in apath past a printing position on said platen, supporting means forflexurally mounting each of said type-bearing elements on said movablemember providing for relative movement with respect to said movablemember of said type-bearing elements toward and away froM said platen,an interposer element disposed in spaced relation with said platen andon the opposite side of said type-bearing elements from said platen,said interposer element being resiliently supported for relativemovement toward and away from a type-bearing element disposed adjacentsaid platen printing position, a hammer disposed adjacent saidinterposer member on the opposite side of said interposer member fromsaid type-bearing elements, and actuating means for moving said hammerto strike said interposer member which in turn is so located as tostrike one of said type-bearing elements on-the-fly as the type-bearingelement is moved by said movable member past said printing position onsaid platen, the movement of said hammer being arrested after saidhammer strikes said interposer member and prior to said interposermember striking said one of said type-bearing elements so that saidinterposer member moves ballistically between said hammer and said oneof said type-bearing elements, each of said type-bearing elements andsaid interposer element being so formed that the mass of said interposerelement is no greater than the mass of each of said type-bearingelements, whereby said interposer element upon striking said one of saidtype-bearing elements will transfer its momentum to said one of saidtype-bearing elements without moving into said path.